1. Field of the Invention
The present invention relates to an image recognition technique, especially, to technique for identifying an individual object.
2. Description of the Related Art
A technique of recognizing an object under various conditions is disclosed in Japanese Patent Laid-Open No. 10-275237. Japanese Patent Laid-Open No. 10-275237 discloses a recognition technique that executes model fitting by detecting a moving region in an image and fitting a geometric model in that region.
A technique disclosed in Japanese Patent Laid-Open No. 2003-263639 registers face images corresponding to various facial directions in advance, calculates the collation scores of an input image with respect to the images of faces in the respective directions, selects a deformation parameter corresponding to a direction with a high collation score, converts the inputted image into a frontal face by using the selected deformation parameter, and collates it with a model image.
A technique examined in Huang et al., “Face Recognition Using Component-Based SVM Classification and Morphable Models” Lecture Notes in Computer Science LNCS2388, Springer-Verlag, 2002, pp. 334-341 generates a three-dimensional CG model from a sensed image, generates face images corresponding to various facial directions, and trains a support vector machine, thereby executing face recognition independent of directions and illumination variations.
In the above-described prior arts, however, it is difficult to efficiently and accurately identify an individual while coping with various states related to the poses, expressions, and illumination conditions of objects (e.g., identical persons) in the same class even when both the number of states and the number of individuals to be identified increase.